Conventionally, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are widely used as coolants, foaming agents, solvents, cleaners, heat transfer mediums, working fluids, reaction solvents, solvents for paints, extractants, dewatering agents, drying agents and the like. However, these materials contain chlorine and are targets of concern as materials that cause depletion of ozone layer. In order to solve such a problem, alternative compounds for CFCs and HCFCs that do not cause depletion of ozone layer even when being released into the atmosphere are desired.
As such alternative compounds, many materials including hydrocarbons (HCs), hydrofluorocarbons (HFCs), hydrofluoroethers (HFEs) and the like have been proposed.
HCs are proposed for a wide range of applications mainly including coolants, foaming agents, solvents, cleaners, heat transfer mediums, working fluids, reaction solvents, solvents for paints, extractants, dewatering agents, drying agents and the like. HC-based materials are advantageous in not exerting much influence on global warming, depletion of ozone layer in the stratosphere or the like. However, most of HC-based materials are flammable and cause concerns regarding safety.
HFCs, which do not contain chlorine atoms, iodine atoms, bromine atoms or any other atoms that cause depletion of ozone layer, do not influence the ozone layer almost at all. However, most of HFCs, which are non-flammable, have a long atmospheric life time and cause concerns regarding influence on global warming.
HFEs, which do not contain chlorine atoms, iodine atoms, bromine atoms or any other atoms that cause depletion of ozone layer, do not influence the ozone layer almost at all. In addition, according to an estimation, HFEs, which contain a plurality of hydrogen atoms, have a relatively high reactivity with an OH radical in the atmosphere and thus have a short atmospheric life time. Therefore, HFEs do not cause much influence on global warming. However, when HFE is used independently, the required performance may not be exerted sufficiently.
In many cases where a plurality of HFEs are mixed (Japanese Laid-Open Patent Publication No. 2005-23259) and in many cases where HFE is mixed with a compound such as alcohol or the like (Japanese Laid-Open Patent Publication No. 2008-133438, Japanese Laid-Open Patent Publication No. Hei 10-324897), properties required of an alternative for CFC, HCFC or the like, namely, compatibility with polyol, coolant characteristics, cleaning characteristics, surface tension, heat conductivity of gas and the like are improved.
However, it is known that when such a mixture is a non-azeotropic-mixture-like composition, the concentration thereof needs to be controlled because the mixture ratio thereof in the form of a vapor and the mixture ratio thereof in the form of a liquid are different from each other. In the case where, for example, the non-azeotropic-mixture-like composition is used for a cleaner and the cleaner is evaporated during cleaning, the mixture ratio of the cleaner is changed and thus a stable operation cannot be easily performed. In the case where the non-azeotropic-mixture-like composition is used for a coolant also, the mixture ratio is changed when the coolant leaks, which lowers the heat pump performance.
By contrast, when such a mixture is an azeotropic mixture-like composition, the concentration thereof does not need to be controlled because the mixture ratio thereof in the form of a vapor and the mixture ratio thereof in the form of a liquid are substantially the same as each other. Therefore, the above-described problems do not occur. However, such a mixture does not always contain an azeotropic mixture-like composition. Whether there is such an azeotropic mixture-like composition or not cannot be estimated.